1. Field of the Invention
Embodiments of the invention generally relate to apparatuses and methods utilized in optics, and more specifically to apparatuses and methods for adaptive optics aberration correction and imaging. The invention disclosed herein relates to a method and system for sensorless adaptive optics that uses an optimization algorithm that is based on a suitable image quality metric to optimize the optical quality in ocular image frames acquired with a confocal adaptive optics scanning laser ophthalmoscope (AOSLO) or other image acquiring devices.
2. Description of the Related Art
Adaptive optics correction of the eye's optical aberrations enables high-resolution ocular imaging and measurement of visual function on a cellular level in living human eyes. Adaptive optics has been successfully incorporated in numerous ocular imaging modalities and has generated great potential for learning about, diagnosing, and treating diseases that impact the retina. Adaptive optics is an emerging technology that can correct for the eye's optical imperfections (or aberrations) to image the living eye and/or deliver vision testing stimuli with high resolution and precision. Adaptive optics has several research and clinical applications in normal and diseased eyes. The clinical importance of adaptive optics continues to grow as the number of scientific and clinical findings it has made possible in the eye continues to increase. Despite this potential, clinical translation and routine use of this technique outside the research laboratory has been slow.
A key feature of current adaptive optics systems for the human eye is a wavefront sensor that measures the eye's aberrations and is coupled in a closed feedback loop to a correcting element, such as a deformable mirror or liquid crystal spatial light modulator. In addition to increasing system complexity and cost, noise and fidelity of the wavefront sensor place a fundamental limit on achievable image quality in current adaptive optics ophthalmoscopes, since accurate aberration correction requires accurate measurement. This fundamental limit may be particularly adverse in the clinical environment, for patients with ocular pathology (such as cataracts or keratoconus), or in any other high noise situation (such as wavefront sensing with restricted light levels). Additionally, the wavefront sensor ‘beacon’ can interfere with visual experiments.
Thus, it would be advantageous to have a wavefront sensorless adaptive optics system for the living eye. However, the living human eye poses several unique characteristics that make it challenging to implement successfully wavefront sensorless adaptive optics techniques. Typically, wavefront sensorless correction methods have been implemented in situations where aberrations and the specimen being imaged are essentially static (e.g., in microscopy). This is quite unlike the situation in the living eye, where aberrations and tear film quality are inherently dynamic and eye movements create constant motion of the retina with respect to the imaging sensor. The dynamics of the eye's aberrations are exacerbated by the difficulty of stabilizing patients' pupils with respect to the optical system, while eye movements create the possibility that differences in intensity due to the spatial structure of the retina could create spurious differences in the intensity metric used for the sensorless control signal. These dynamics are especially problematic given the relatively large number of iterations that are desired for correction with sensorless methods. One of the current challenges in implementing wavefront sensorless adaptive optics in the human eye (given the temporal dynamics inherent in the eye's aberrations, which are not typically present in microscopy and other photonic engineering applications) is its relatively slow convergence speed. Blinking presents an additional challenge for effective sensorless adaptive optics methods.
Therefore, there is a need for improved apparatuses and methods for adaptive optics imaging, especially for apparatuses and methods suitable for the human eye.